Buy map when needed

Maps cost! And casual gamers could possibly forget whether they've explored everything.
The Buy map button is now disabled if the whole map has been seen (yes, even a single uncovered tile is enough).

script/events/room.js

@@ -433,6 +433,20 @@ Events.Room = [
 					'buyMap': {
 						text: _('buy map'),
 						cost: { 'fur': 200, 'scales': 10 },
+						available: function() {
+							var mask = $SM.get('game.world.mask');
+							var dark = false;
+							loop:
+							for(var i = 0; i < mask.length; i++) {
+								for(var j = 0; j < mask[i].length; j++) {
+									if(!mask[i][j]) {
+										dark = true;
+										break loop;
+									}
+								}
+							}
+							return dark;
+						},
 						notification: _('the map uncovers a bit of the world'),
 						onChoose: World.applyMap
 					},